Find: Twitter’s mobile web app delivers performance

As the number of people using Twitter has grown, we've wanted to make sure that we deliver the best possible experience to users, regardless of platform or device. Since twitter.com is not optimized for smaller screens or touch interactions familiar to many smart phones, we decided to build a cross-platform web application that felt native in its responsiveness and speed for those who prefer accessing Twitter on their phone's or the tablet’s browser.

A better mobile user experience

When building mobile.twitter.com as a web client, we used many of the tools offered in HTML5, CSS3, and JavaScript to develop an application that has the same look, feel, and performance of a native mobile application. This post focuses on four primary areas of the mobile app architecture that enabled us to meet our performance and usability goals:

event listeners

scroll views

templates

storage

Twitter's mobile app architecture

Event listener

For the Twitter application to feel native, responses have to be immediate. The web application delivers this experience by using event listeners in its code.

Traditionally, Javascript uses DOM-only events such as onclick, mouseover, mouseout, focus, and blur to render a page. However, because Twitter has so many unique points of interaction, we decided to optimize the resources presented to us with mobile devices. The web application we developed uses event listeners throughout the code. These syntactic events, loaded with the JavaScript on the client, listen for unique triggers that are fired, following the users’ interactions. When users retweet or favorite Tweets, the JavaScript listens for those events and responds accordingly throughout the application, updating screen views where necessary.

The client-side JavaScript on the mobile application handles communication with Twitter through the Twitter API. To illustrate the use of event listeners, let’s look at how a Retweet works. When a user clicks the Retweet button on the UI, the system fires a click event that fires a Retweet request through the API.

The web client application listens for an event like a Retweet and updates the rest of the application when it receives it.

When that Retweet event is successful, a return event fires off a signal and the web app l...